Add (failing) test for slice-to-array-pointer conversion added in Go 1.17

flimzy · flimzy · commit c5706c364eeb · 2021-08-05T11:29:16.000+02:00
diff --git a/tests/slice_to_array_ptr_test.go b/tests/slice_to_array_ptr_test.go
@@ -0,0 +1,55 @@
+package tests
+
+import "testing"
+
+func TestSliceToArrayPointerConversion(t *testing.T) {
+	// https://tip.golang.org/ref/spec#Conversions_from_slice_to_array_pointer
+	s := make([]byte, 2, 4)
+	s0 := (*[0]byte)(s)
+	if s0 == nil {
+		t.Error("s0 should not be nil")
+	}
+	s2 := (*[2]byte)(s)
+	if &s2[0] != &s[0] {
+		t.Error("&s2[0] should match &s[0]")
+	}
+	r := func() (r interface{}) {
+		defer func() {
+			r = recover()
+		}()
+		s4 := (*[4]byte)(s)
+		_ = s4
+		return nil
+	}()
+	if r == nil {
+		t.Error("out-of-bounds conversion of s should panic")
+	}
+
+	(*s2)[0] = 'x'
+	if s[0] != 'x' {
+		t.Errorf("s[0] should be changed")
+	}
+
+	var q []string
+	q0 := (*[0]string)(q)
+	if q0 != nil {
+		t.Error("t0 should be nil")
+	}
+	r = func() (r interface{}) {
+		defer func() {
+			r = recover()
+		}()
+		q1 := (*[1]string)(q)
+		_ = q1
+		return nil
+	}
+	if r == nil {
+		t.Error("out-of-bounds conversion of q should panic")
+	}
+
+	u := make([]byte, 0)
+	u0 := (*[0]byte)(u)
+	if u0 == nil {
+		t.Error("u0 should not be nil")
+	}
+}
